I am totally new to C. I want to re-prompt when the input value is not a number and when it's a number it should be less than 1. when I give any sort of string it works correctly. But when I give any number it goes to the next line without printing "Number: ".Then in the next line, it prints "Number: "again if the input value is less than 1.
int x;
printf("Number: ");
while (scanf("%d", &x) != 1 || x < 1 )
{
printf("Number: ");
scanf("%*s");
}
and the result it gives me is this
It would be wise to use fgets to read the line, then use sscanf to parse the input. That way, you can get the line, then check if sscanf succeeds!
Simple example:
int target_number; // The number you will have at the end of this.
while (1) { // Loop for rechecking number
char line[16]; // See notes on how to read the whole line.
fgets(line, sizeof(line), stdin);
// We use 1 here because sscanf returns the number of format specifiers that are matched. Since you only need one number, we use 1.
if (sscanf(line, "%d", &target_number) != 1) {
fprintf(stderr, "Invalid Input! Please enter in a valid number.");
continue;
}
}
// Do whatever you will with target_number
You can see how to read the whole line here.
It does not protect against buffer overflow attacks and the like. Please see this on the right way to do this. If this is just for learning, you don't need to worry.
/*This is how it will work the way you want.
If I understand your goal correctly, of course?
If your goal was different,
please specify and I will try to solve it.*/
#include<stdio.h>
int main(void)
{
int x;
printf("Number: ");
while (scanf("%d.%*d", &x)!=1 || x<0)
{
if(x<0)
{
printf("Number: ");
continue;
}
else
printf("Number: ");
scanf("%*s");
}
printf("Hello world!");
return 0;
}
